1 Review List the conclusions that Griffith and Avery drew from their experiments

1

• 1 Review List the conclusions that Griffith and
  Avery drew from their experiments
• Identify Variables What experimental variable
  did Avery use when he repeated Griffiths work
• 2 Review What conclusion did Hershey and Chase
  draw from their experiments
• Infer Why did Hershey and Case grow viruses
  in cultures that contained both radioactive
  substances? What might have happened if they only
  used one radioactive substance
• 3 Choose Griffith, Avery, or Hershey and Chase
  and develop a flow chart that shows how they used
  various scientific methods. You may want to refer
  to Ch 1 for descriptions of the scientific method.

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Ch 12 DNA

• 12.1 Identifying the Substance of Genes

3
Frederick Griffith

• Two different strains of same bacteria one
  strains caused pneumonia
• Grew both in culture plates.

4

• Griffith injected mice with disease-causing
  bacteria, the mice developed pneumonia and died
• He injected mice with harmless bacteria, the mice
  stayed healthy.

5

• Griffith took a culture of the S strain, heated
  the cells to kill them, and then injected the
  heat-killed bacteria into laboratory
• Mice survived.

6

• He mixed the heat-killed, S-strain bacteria with
  live, harmless bacteria from the R strain and
  injected it into laboratory mice
• Injected mice developed pneumonia, and died.

7

• Some chemical factor changed harmless bacteria
  into disease-causing bacteria was transferred
  from the heat-killed cells of the S strain into
  the live cells of the R strain.

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Transformation

• Process where one strain of bacteria is changed
  by a gene from another strain of bacteria.

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Avery

• Extracted a mixture of various molecules from the
  heat-killed bacteria
• Added enzymes that broke down proteins, lipids,
  carbohydrates, and RNA
• Transformation still occurred.

10

• Averys team repeated the experiment using
  enzymes that would break down DNA
• Transformation did not occur
• DNA is the transforming factor.

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Hershey and Chase

• Experiment with bacteriophages
• Confirmed Averys results .

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Bacteriophages

• Virus that infects bacteria
• Attaches to the surface of the bacterial cell
• Injects its genetic
• information
• New bacteriophages
• are produced.

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Hershey-Chase Experiment

• What part of the virus - the protein coat or the
  DNA core - entered the bacterial cell.

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Hershey-Chase Experiment

• Grew viruses in cultures containing radioactive
  isotopes of phosphorus-32 (P-32) sulfur-35
  (S-35)
• Proteins contain almost no phosphorus and DNA
  contains no sulfur.

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• If they found S-35 in the bacteria then the
  viruss protein coat had been injected into the
  bacteria
• If they found P-32 then the DNA core had been
  injected
• They mixed the marked viruses with bacterial
  cells.

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• In the bacteria they found phosphorus P-32 , the
  marker found in DNA
• DNA was the genetic material.

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The Role of DNA

• Capable of storing, copying, and transmitting
  genetic information in a cell.

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Storing Information

• Main job is of DNA is to store information
• Genes control patterns of development.

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Copying Information

• Before a cell divides, it must make a complete
  copy of its genes.

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Transmitting Information

• When a cell divides each cell receives a complete
  copy of the genetic information
• Loss of any DNA during meiosis might mean a loss
  of valuable genetic information.